Handles SHT3C sensor

...And this is the first time I'm flashing the firmware into a real
b-parasite board!

code/b-parasite/config/prst_config.h

@@ -4,7 +4,7 @@
 #include "nrf_gpio.h"
 
 // Built-in LED.
-#define PRST_LED_PIN NRF_GPIO_PIN_MAP(1, 11)
+#define PRST_LED_PIN NRF_GPIO_PIN_MAP(0, 28)
 
 // Deep sleep.
 #define PRST_DEEP_SLEEP_IN_SECONDS 2

code/b-parasite/src/main.c

@@ -72,11 +72,13 @@ static void rtc_callback() {
   prst_adv_stop();
   nrf_gpio_pin_clear(PRST_LED_PIN);
   UNUSED_VARIABLE(batt_read);
-  UNUSED_VARIABLE(temp_humi);
+  // UNUSED_VARIABLE(temp_humi);
   NRF_LOG_INFO("Read batt: " NRF_LOG_FLOAT_MARKER " V (%d), %u mV",
                NRF_LOG_FLOAT(batt_read.voltage), batt_read.raw, batt_read.millivolts);
   NRF_LOG_INFO("Read temp: " NRF_LOG_FLOAT_MARKER " oC",
                NRF_LOG_FLOAT(temp_humi.temp_c));
+  NRF_LOG_INFO("Read humi: " NRF_LOG_FLOAT_MARKER " %%",
+               NRF_LOG_FLOAT(temp_humi.humidity));
   NRF_LOG_FLUSH();
 }
 

code/b-parasite/src/prst/ble.c

@@ -9,6 +9,9 @@
 
 #include "prst_config.h"
 
+// TODO(rbaron): More info in the adv packet:
+// - Software version
+
 // We need to pick a service UUID for broadcasting our sensor data.
 // 0x181a is defined as "environmental sensing", which seems appopriate.
 #define SERVICE_UUID 0x181a

code/b-parasite/src/prst/shtc3.c

@@ -3,62 +3,52 @@
 #include <app_error.h>
 #include <nrf_delay.h>
 #include <nrf_drv_twi.h>
-#include <nrf_gpio.h>
 #include <nrf_log.h>
 #include <nrf_log_ctrl.h>
 
-// #define PRST_SHT3C_DEFAULT_ADDR 0x70
-// I'm using a sht30 to test while I wait for the new PCBs.
-#define PRST_SHT3C_DEFAULT_ADDR 0x44
-
 static const nrf_drv_twi_t twi_ = NRF_DRV_TWI_INSTANCE(0);
 static nrf_drv_twi_config_t twi_config_ = NRF_DRV_TWI_DEFAULT_CONFIG;
 
 static uint8_t buff[6];
 
+static void write_cmd(uint16_t command) {
+  uint8_t cmd[2];
+  cmd[0] = command >> 8;
+  cmd[1] = command & 0xff;
+  APP_ERROR_CHECK(nrf_drv_twi_tx(&twi_, PRST_SHTC3_ADDR, cmd, 2,
+                                 /*no_stop=*/false));
+}
+
 void prst_shtc3_init() {
-  twi_config_.scl = NRF_GPIO_PIN_MAP(0, 3);
-  twi_config_.sda = NRF_GPIO_PIN_MAP(0, 2);
-  // twi_config.clear_bus_init = true;
+  twi_config_.scl = PRST_SHT3C_SCL_PIN;
+  twi_config_.sda = PRST_SHT3C_SDA_PIN;
   twi_config_.frequency = NRF_TWI_FREQ_100K;
 }
 
 prst_shtc3_read_t prst_shtc3_read() {
-  uint32_t err_code;
-  // Sends request for data with clock stretching. Currently not working
-  // very well - sometimes it works, sometimes the read blocks forever.
-  // uint8_t tx_data[] = {0x2c, 0x06};
-  // Request for data withour clock stretching. If no data is available yet,
-  // the result will be a NACK.
-  uint8_t tx_data[] = {0x24, 0x00};
-
-  err_code = nrf_drv_twi_init(&twi_, &twi_config_, NULL, NULL);
-
-  APP_ERROR_CHECK(err_code);
-  nrf_delay_ms(10);
+  APP_ERROR_CHECK(nrf_drv_twi_init(&twi_, &twi_config_, NULL, NULL));
   nrf_drv_twi_enable(&twi_);
-  nrf_delay_ms(10);
-  err_code = nrf_drv_twi_tx(&twi_, PRST_SHT3C_DEFAULT_ADDR, tx_data,
-                            sizeof(tx_data), false);
-  APP_ERROR_CHECK(err_code);
 
-  // TODO(rbaron): timeout.
-  while (true) {
-    err_code = nrf_drv_twi_rx(&twi_, PRST_SHT3C_DEFAULT_ADDR, buff, 6);
-    if (err_code == NRF_ERROR_DRV_TWI_ERR_ANACK) {
-      nrf_delay_ms(10);
-      continue;
-    }
-    break;
+  // Wake the sensor up.
+  write_cmd(PRST_SHTC3_CMD_WAKEUP);
+  nrf_delay_ms(1);
+  // Request measurement.
+  write_cmd(PRST_SHTC3_CMD_MEASURE_TFIRST_LOW_POWER);
+  // Read temp and humidity.
+  while (nrf_drv_twi_rx(&twi_, PRST_SHTC3_ADDR, buff, 6) != 0) {
+    nrf_delay_ms(10);
   }
+  // Put the sensor in sleep mode.
+  write_cmd(PRST_SHTC3_CMD_SLEEP);
 
-  // TODO(rbaron): put the sensor to sleep & save power.
-
+  // Uninit i2c.
   nrf_drv_twi_uninit(&twi_);
+
   NRF_LOG_INFO("Computing...");
   double temp_c =
       -45 + 175 * ((double)((buff[0] << 8) | buff[1])) / ((1 << 16) - 1);
-  // double humi = 100 * ( (double) ((buff[0] << 8) | buff[1])) / ((1<<16) - 1);
-  prst_shtc3_read_t ret = {.temp_c = temp_c, .humidity = 0};
+  double humi = 100 * ((double)((buff[3] << 8) | buff[4])) / ((1 << 16) - 1);
+
+  prst_shtc3_read_t ret = {.temp_c = temp_c, .humidity = humi};
   return ret;
 }

code/b-parasite/src/prst/shtc3.h

@@ -1,6 +1,17 @@
 #ifndef _PRST_SHT3C_H_
 #define _PRST_SHT3C_H_
 
+#include <nrf_gpio.h>
+
+#define PRST_SHT3C_SDA_PIN NRF_GPIO_PIN_MAP(0, 24)
+#define PRST_SHT3C_SCL_PIN NRF_GPIO_PIN_MAP(0, 13)
+
+// Values from the SHTC3 datasheet.
+#define PRST_SHTC3_ADDR 0x70
+#define PRST_SHTC3_CMD_SLEEP 0xb098
+#define PRST_SHTC3_CMD_WAKEUP 0x3517
+#define PRST_SHTC3_CMD_MEASURE_TFIRST_LOW_POWER 0x609c
+
 typedef struct prst_shtc3_values {
   double temp_c;
   double humidity;